Monday, February 24, 2014

Tube Review: The Mullard XF2 EL34 pentode

Introduction:
The Mullard EL34 - though perhaps not the best sounding of this family of tubes - is famous for a big and rich sound favored by guitarists and hi-fi nuts.  The XF2 version, like many early tubes, has welded plates, along with that thick, dark getter that is a trademark of the valves that rolled out from the Blackburn factory.  Later ones have similar construction but used crimped plates - I've never sat down and compared the different XF models, but needless to say they're all pretty good.

 The Mullard "sound", for whatever reason, has always been on the darker scale than neutrality.  Perhaps there is some secret mojo in the cathode chemistry or the metal quality, but this sound difference is easily noticeable in comparison to an original Philips EL34 or even any modern EL34.  This romantic sound, in the wrong amplifier, can lead to a syrupy sound - I'm thinking of something like a stock Dynaco 70 or any vintage amplifier with weak power supply capacitors and/or oil coupling capacitors.  So, like anything else, system balance is important.

The pair of Mullard XF2 EL34s I'm reviewing here are high mileage units pulled from my Eico HF-60 monoblocks.  Though they have plenty of hours on them, they still test almost as new - longevity is something that vintage tubes seem to do well and is needed, especially when running in something as abusive as the HF-60.  For this amplifier with a plate voltage of 400VDC and a screen of 250VDC, 60mA was chosen as a nice cruising speed.

Listening Tests:
The Immortal Otis Redding has a nice and punchy sound, albeit a tad stripped down.  The Mullards conveyed this simple recording with excellent clarity, depth, and dynamics.  Otis's voice sounded very natural as did the instrumentation.  The sound never became harsh or strident with this output tube.  There was also a nice projection to the vocals, pushing the sound beyond the speakers.  This seems to be a trait of vintage tubes - an enveloping sound with a 3-D effect: layered depth, wide and stable imaging, and a sense of being tangibly involved in the music.

Frank Sinatra - Sinatra at the Sands appears to be a three channel recording with instrumentation on the left and right with Frank right in the middle of the action.  The dynamics - on the right system - are truly breathtaking.  The Mullard EL34 excelled here, sounding almost as big as the Tung Sol 6550.  On the quieter songs like Don't Worry 'bout Me, all the emotion came through with the sensitivity that only Sinatra could surprisingly pull from that playboy act.

The last record in this listening test was Steely Dan - Aja which is a modern recording with deep bass, shifting dynamics, and crafty compositions.  The Mullard EL34 wonderfully captured the trailing edges of the reverberation and gave a soundstage that was big and organic.  The instruments floated nicely in space too.  There was a touch of darkness to the music, giving a not quite neutral sound compared to a Tung Sol 6550 or the ultra-vividness of the Philips metal base.

Conclusion:
The Mullard EL34, compared to the new production tubes I've heard, has a real magic.  The music flows with more ease - a naturalness that is hard to describe, but the sound that is reproduced is cut from the same cloth in a grain-free way that makes me forget that I'm listening to a stereo.  Even the Shuguang GEKT88 - which is very good - doesn't capture this ability of convey the real soul of the recording.

However, the Mullard is not the most hyper-detailed and bends the signal to a darker, more romantic spectrum.  But this is a nice place to be - especially in the world of hot digital recordings and aggressive moving-coils.  If you're searching for the most transparent or an abundance of detail, then this may not be the tube for you.  But - and this varies from listener to listener - any sins are easy to forgive.  This is a tube for the music lover, not the nitpicker. 

Thursday, February 20, 2014

Review: Nakamichi SR-3A receiver


For some strange reason I decided to simplify the second system, replacing the odd couple Rotel integrated and Sansui tuner with a receiver.  Now I've never been a big fan of the "all in one box" approach to audio components, but having a single device handle the amplification chain and radio certainly takes up less space than all separates.  After cruising through several hundred items on Ebay, I finally zeroed in on a Nakamichi SR-3A receiver.  Why?  It uses a "Stasis" output stage, the very same topology that my now departed Threshold S/500 had.  This circuit was designed by the great Nelson Pass who continues to make some of the most interesting amplifiers around.  Though obviously built to a price point and lacking the muscular grunt of the Threshold, I thought the Nakimichi would provide good enough service for less intensive listening.

When I received the package, I opened the box and found a rather Plain-Jane receiver in that most boring of colors: black.  Hooking it up was a bit of a nightmare - the receiver depth is larger than expected, making speaker and RCA cables with large jacks almost impossible to fit because of the limited Ikea Expedit shelf space.  Also the banana jacks in the back really don't have any metal contact and are too small for the banana plug(!).  So in the end I ended up using insulated wire twisted together.  Other than that, build quality is pretty good - though not exactly McIntosh.

Once I finally had everything in place, I could finally turn the Nakamichi on.  There is a fairly dim display for the radio station, tuner signal strength, and that's about it for the light display.  There is an input for turntable (with a switch for MM and MC), CD, Video, and Radio.  The tuner portion is switchable between AM and FM (no surprise there) and stations can be programmed into memory.  Bass and Treble controls are defeatable.  There is a loudness contour button and two speaker selections: A or B.  The right side is dominated by a volume and balance combination - the inner ring controlling the former while the outer ring does the latter.


Listening to a record, the sound coming out of my B&W Matrix 805 speakers took on a different character.  The mids were cleaner and leaner, but, strangely enough, the lowest bass seemed to have more depth and control.  The top end had real "presence" - ie, slightly forward in it's presentation.  The phono section itself seemed to be very good with excellent overload characteristics and lacking that op-amp etch that many receivers have.  Though only rated at 45WPC, the Nakamichi SR-3A seemed to punch much higher than one would expect.  There was more than enough volume for my not-quite efficient B&W speakers and mid-sized room.   Dynamic contrasts were also more evident, making this receiver a good match for these classic monitors.

The tuner - which is popular for listening to classical music - was excellent.  I'm normally not a fan of digital tuning, but the Nakamichi really locked into the signal, easily bettering my analog Sansui AU-777.  Music from the radio also seemed more lively compared to my old integrated/tuner combination.

In conclusion, the Nakamichi SR-3A is one of the better "vintage" receivers I've heard.  It certainly doesn't sound overly warm or suffer from solid-state harness.  Instead, it's quite even-handed, even with my finicky B&W tweeters.  The Stasis output circuit really does remind me of a mini-Threshold amplifier; giving the user a taste of the real high-end.  Highly recommended.

Second System:
Analog: Dual CS5000 turntable
Digital :Pioneer DVD-V7400
Speakers: B&W Matrix 805s on stands
Wire: Various brands

Tube Review: The Shuguang EL34B pentode


Introduction:
Ah - the legendary EL34 pentode which has been the heart and soul for classic guitar rigs and my first ever tube amplifier, the Dynaco 70.  Developed (with several ancestors) by Philips for PA use, this slim bottle cannot be mistaken for any other tube out there.  Lately this tube - at least in some quarters - has gotten a bad rap as being too warm or not a real audiophile contender, unlike the 6550/KT88 or even (ha!) the 6L6 family.  I strongly disagree with this, thinking the EL34 is one of the most musical tubes out there, walking a fine line between a triode romance and warmth, and the more dynamic sound of the 6550.

The Shuguang "B" version of the EL34 is the stock tube in countless amplifiers and has been labeled Ruby, Valve Art, and who know what else.  It's quite common for new owners to ditch these tubes for something more upscale from the Russians, like the EH, Tung Sol or Genalex "re-issues", or even something NOS like Siemens or Mullards.

There is also the conception that Chinese tubes are prone to blowing up - perhaps a leftover memory from the days of the Jadis JA200 when the Golden Dragon KT88s were referred to as firecrackers.  At least with my experience using the EL34B tube, I've put the hurt on them with the Eico HF-60 monoblocks.  Each tube was consistently taking 500VDC on the plate at 60mA.  That's right on the edge of max dissipation but I never had one blow up.  I'm not sure what modern tube I would trust to take that kind of abuse.

Just for fun, replaced the GEKT88's in the Multi-Valve amplifier with a pair of used and abused Shuguang EL34s from my junk box.  I set the bias point at 60mA which seemed to be the sweet spot.


Listening Test:
For amplifier warmup I listened to my very rare copy of These Immortal Souls - Get Lost (Don't Lie) which has big heavy drums and the chilling guitar work of the ex-Birthday Party member Rowland S. Howard.  The sound is naturally dark and dirgey - this is no audiophile recording - but still incredibly enjoyable.  The bass was big with tons of impact and slam while the midrange had a nice tube "glow" that added to the musical experience.  The treble did, however, seem a tad rolled-off which may or may not be a good thing depending on your speakers.

Neil Young - Live at Massey Hall is a great sounding record.  With the EL34Bs in place I heard plenty of warmth - a bit excessive - that could be a rough analog of the classic Mullard sound.  Where the Mullard still manages to have good detail, the Shuguang lacked in this department.  It wasn't actively annoying - more a sin of omission - but just don't expect to hear everything on the recording.  Nonetheless, Neil Young's voice and guitar work were very natural sounding.  It was the hall reflection and some of the minor audience sound that went missing.

For something more dynamic, I tried out Classic Records re-issue of The Who - Tommy.  The bass and dynamics were very good, but the darkness/warmth was enough to cloud the instrument shimmer, resulting in a less exciting sound.  Depth and instrument placement weren't bad, but nothing close to a vintage Tung Sol 6550 where the images float beyond the boundary of the speakers.  Instead you are left with a closed experience - reminding me of a stock Dynaco 70 that needs to be re-tubed and re-capped - still pleasant but not the ultimate in fidelity.

Conclusion:
The Shuguang EL34B makes no pretenses of being state of the art, but it is a good working man's tube - and being available at ridiculously low prices can be used and abused without too much concern.  These obviously don't have the greatest cathode or metallurgy so tube life on these isn't the longest either.  However if you have an old Dynaco 70 laying around or need to retube a friend's Marshall, the Shuguang EL34B is not a bad choice.  I certainly prefer its presentation over that of the Electro-Harmonix (thin bottle) EL34 which, in comparison, sounds like a bad solid-state amplifier.  As always, YMMV.

Review System:
VPI Aries with JMW 10.5i tonearm and SDS Power Supply
Dynavector 10X5
Cardas Cross 1M interconnects
Quicksilver preamplifier with Mullard short-plate 12AX7s, RCA 12FQ7s, Amperex 12AU7
Cardas Quadlink 5C 1M interconnects
Multi-Valve Stereo amplifier
Cardas Hexlink speaker cable
UREI 813A monitor speakers
VTI BL503 equipment rack 

Tuesday, February 18, 2014

Tube Review: The Shuguang GEKT88 tetrode

Introduction:
The KT88 was GEC's answer to Tung Sol's big dog 6550, the most powerful consumer output tube at the time.  The '88 boasted even higher plate and screen voltages, the latter an important consideration for Ultralinear output stages.  The KT88 was used in some of the more powerful amplifiers of the time - the Dynaco Mark III, the Harman-Kardon Citation II, the Scott LK-150 - back when 50 or 60Ws was considered an insane amount of power for driving your efficient horn speakers.

Of course times goes on and new technology comes along - instead of a 60lb amplifier with massive output transformers and making enough heat to fry an egg, the consumer can get a cool running amplifier for way less money and in a considerably lighter package.  But even then there are a cohort of audiophiles who won't give up valves since they have an interest in a colorful and lively presentation when listening to their music.

The GEKT88 - also sold as a Penta KT88SC - is rumored to be Shuguangs direct copy of the now incredibly expensive GEC original.  I don't have an original on hand - this was a tube that I never had much interaction with even in the early 90s - so I can only compare by images.  Hmm... solid-plate, getters on the side, similar mica location... bulb structure is slightly different.  The rumor is that Shuguang is using the actual GEC machinery and some ancient batch of cathode emulsion.  Perhaps that's true, but how do they sound?  There was only one way to find out: I ordered a pair via Ebay and waited four weeks for them to arrive from China.

After some time in the Multi-Valve amplifier, dialed in at 70mA each, it was time to do some serious listening.

Listening Tests:
Since Neil Young - Live at the Cellar Door is one of the newest entries to my record collection, I decided to give this the first spin.  The GEKT88 proved itself right from the get go with a big clear sound with plenty of body in the guitar and piano.  The vocals are right in the middle of the speakers and project out much like the real thing.  The coughs and wheezes of the audience weren't lost in any background smear nor did they stick out in an unnatural way with some false heightened detail.  On the song Expecting to Fly, Neil really pounds those piano keys and all that power comes through in a natural way.  So far I'm quite impressed, but this is an album without bass or drums, so I thought it was time to move on to something even more dynamic.

My UK pressing of Supertramp - Crime of the Century is not as bold sounding as my U.S. one, but is a tad smoother.  With the GEKT88s in place, the bass went down real deep with plenty of impact.  Image depth was about real close to the best NOS stuff I've heard while side-to-side soundstaging was excellent.  What this new production tube seems to lack is just that last bit of true greatness I hear with vintage Tung Sol 6550s or Dutch Philips EL34s.  It's very close, but there is some faint but audible grain in the upper mids.

Fleetwood Mac - self-titled was up next.  The vocals were nice and smooth and the multi-tracking of the drums was very obvious.  Though this is a "busy" recording, it is still easy to pick out individual instruments in the mix.  Stevie Nick's voice was sublime with some real emotion coming through.  Very nice.

My promo copy of Earth, Wind & Fire - All 'N All is a hot - and I mean aggressive - recording - with plenty of top-end.  This came through with out any rolled-off treble or excessive tube "warmth"..  The bass and the thwack of the drum started and stopped without any overhang.  It was also easy to pick out different vocalists in the chorus.  A fun and engaging album, the sound came through with great clarity.  I've heard this album done better - like through the Eico HF-60s with their seemingly unlimited power - but the GEKT88s in the Multi-Valve amp were a close runner-up.

Conclusion:
As far as new production power tubes go, the GEKT88 is the best I've heard - so far.  Of course there will be other reviews coming up, so stay tuned.  Needless to say this Shuguang power tube really captures 90% of the magic of NOS, only failing at the very edges that still makes me prefer the vintage stuff.  Of course I am talking about that last bit of inner detail, liveliness, and that sense of being totally immersed in the stereo experience.  Nonetheless I give these tubes a high recommendation.


Review System:
VPI Aries with JMW 10.5i tonearm and SDS Power Supply
Dynavector 10X5
Cardas Cross 1M interconnects
Quicksilver preamplifier with Mullard short-plate 12AX7s, RCA 12FQ7s, Amperex 12AU7
Cardas Quadlink 5C 1M interconnects
Multi-Valve Stereo amplifier
Cardas Hexlink speaker cable
UREI 813A monitor speakers
VTI BL503 equipment rack  

Saturday, February 15, 2014

Tube Review: The Reflektor 6P3S-E power tetrode and the Sovtek 5881


Introduction:
Way back in my college days, I used to own a Harman-Kardon Citation V amplifier, which was supposed to use 7581 output tubes.  At the time those were rarer than GEC KT66s, so I ended up running RCA black-plate 6L6GCs which had the misfortune of being on the edge of their max dissipation.  A red line would appear right along the plate seam, at the time making me nervous as hell.  The only inexpensive tube that could take the heat was the newly introduced Sovtek 5881.  It wasn't the best sounding tube but it certainly could take the abuse.

The 1970s era 6P3S-E - except for the shinier getter - looks exactly the Sovtek 5881, but the former has become a sort of budget audiophile darling while the latter is known as a rugged guitar tube.  I was curious to see how the 6P3S-E would sound, and at roughly $24 shipped for a pair, I thought it was a perfect tube to try out in the Multi-Valve amplifier which had adjustable fixed bias - needed for dialing in a larger number of popular octal power valves.

Since I also have a pair of newer 5881s on hand, I also decided to compare the two.  Physically they appear to be the same tube - rather business-like - but perhaps the cathode chemistry or even the plate metal quality is different enough to make a real world difference.  Let's find out!

Note: 6P3S-Es were burned in for approximately fifty hours before listening.  The Sovtek 5881s have been used for regulator service and for testing new amplifiers - hours are unknown but definitely more than a hundred.

Listening to the 6P3S-E:
Blue Nile - Hats is a rare vinyl treat with swooping synthesizers and melancholy lyrics.  It isn't the most natural sounding album but has great dynamics and a dramatic soundstage.  Through the 6P3S-E, there seemed to be a touch of iciness - perhaps an artifact of the recording - but I've heard more richness with other output tubes, notably many NOS units like the Mullard EL34 or the Tung Sol 6550.  But still, the 63PS-E has a good transparency which will be loved by many modern music listeners who grew up with solid-state gear.

Next up was the half-speed master of Willie Nelson - Stardust.  Detail was very good, though not the best I heard.  It was the kind of fake detail caused by excessive treble.  Once again I was reminded of a good, but slightly aggressive solid-state amplifier.  Perhaps this tube would be a better match with some paper tweeters or a dull front end, but with a horn tweeter and a moving-coil cartridge the sound was rather forward.  Bass depth and control, however, was quite good as was transparency.  I wish I could combine the 6P3S-E with the darker sound of a Mullard XF2 EL34.  That would give a more ideal tube.

I dug out my copy of Steely Dan - Pretzel Logic and gave it a spin.  The treble energy didn't seem as hot on this album, but once again I heard a slight sterility to the sound.  It wasn't bad - but the 6P3S-E seemed to falsely increase detail by cranking up the treble, adding some glassiness.  The sound didn't really breathe at least not with the musicality I expect from the very best of the NOS tubes.  I didn't get carried away with the music either, not even the soaring vocals of the song Barrytown.


Listening to the Sovtek 5881:
After some warmup I started with side two of The Grateful Dead - Terrapin Station, which is a very unique "rock opera" type piece.  Once again the forward nature of this tube was evident.  I'm thinking if I had an A/B switch box I wouldn't be able to tell the difference between this and the 6P3S-E.  It had the same tipped up top-end, clean mids and good bass control.

In the right system, Cat Power - Jukebox has a big "you are there" sound.  With the 5881, the effect was lessened, losing some of the inner-detail and the lowest, full bass.  Again, it was good but the big DEPTH was shortened, making a flatter, less involving soundstage without the shimmer and swirl of the best output tubes.  If there were differences between this and the 6P3S-E, they were incredibly minor.  Just to be sure, it was time to return to a record I have already listened to.

Once again I gave Willie Nelson - Stardust a listen.  Perhaps it was listener fatigue or system break-in, but I would swear the treble was actually tamer than the 6P3S-E.  The mids were also a tad richer too.  Both tubes, however, were still cut from the same sonic cloth - perhaps the difference between a Mullard XF2 and a XF3: different but not extremely so.

Conclusion:
The 63PS-E or Sovtek 5881 aren't bad tubes, but they aren't great tubes.  They certainly aren't very neutral, hewing to a brighter sound than I like.  They have a forward "in your face" sort of character that may be a better match for vintage speakers or certain MM cartridges.  At least in my system, I wouldn't use them - not while I'm running compression driver/horn tweeters and a moving-coil cartridge.  They are, however, recommended for budget audiophiles, but with serious system matching caveats.  As always, YMMV.


Review System:
VPI Aries with JMW 10.5i tonearm and SDS Power Supply
Dynavector 10X5
Cardas Cross 1M interconnects
Quicksilver preamplifier with Mullard short-plate 12AX7s, RCA 12FQ7s, Amperex 12AU7
Cardas Quadlink 5C 1M interconnects
Multi-Valve Stereo amplifier
Cardas Hexlink speaker cable
UREI 813A monitor speakers
VTI BL503 equipment rack 

Tube Review: The Valve Art 350B pentode


Introduction:
The original Western Electric 350B - which I've only heard in a few rare instances - has become one very expensive output tube.  Valve Art, through Shuguang, currently makes a "reproduction" that is extremely affordable and has a nice vintage "G" bulb shape that would look quite good in a pair of Quad II monoblocks or any other vintage amplifier that can handle the extra filament current of the 350B over the more pedestrian 6L6GC.

I purchased a pair of Valve Art 350B from Antique Electronic Supply.  Price is less than $40 a pair, which is quite inexpensive compared to the majority of NOS and even new tubes.  Construction quality is quite high with  welded plates, good looking mica, two vertical support rods, and white ceramic spacers.  No, it isn't anything like a 1940s 807, but it looks pretty close - perhaps if you rubbed off the Valve Art logo it could fool some of your more tube savvy friends... or not.

I plugged the 350Bs into my Multi-Valve amplifier which has adjustable fixed bias.  I dialed them in at a healthy 60mA, perhaps 50mA would be a safer bet for long life, but at this price I'm willing to give up a little longevity for a few (and I mean a very few) extra watts.  After all, I'm not running horn tweeters in a multi-amp system, but a pair of full-range speakers that can take whatever I can dish out.  At this bias setting there was no sign or red plating and the tubes have been working perfectly after a good solid 100 hours or more.  So much for the myth of poor Chinese tube reliability. 

Listening:
The first record up was Neil Young - Live At The Cellar Door.  Detail - audience coughs and  hall ambiance were all there - perhaps lacking compared to the best NOS I've heard, notably the Philips metal base EL34s and vintage Tung Sol 6550s.  However no frequency aberration stuck out and there didn't seem to be any of the "solid state in a bottle" bleaching that is often the hallmark of new production tubes.  This recording, however, is not the most dynamic so it was time to move on to something else.

My Japanese pressing of The Police - Synchronicity is an exciting and bouncy album requiring plenty of power to unravel everything that is going on.  With the Valve Art 350Bs, I noticed that the bass didn't go as low as the vintage Tung Sol 6550s.  The 350B sounded compressed and confused on the big peaks - perhaps hitting the edge of their power envelope in this single-ended amplifier.   A more efficient speaker could perhaps ameliorate this issue.  I also noticed a touch of dryness - though maybe this is a function of the recording itself.

Pink Floyd - Animals is a perennial favorite of mine - my German pressing is very dynamic with tons of detail.  With the Valve Art 350B, I noticed a murkiness to the sound as if a layer of gauze was making the finer detail and attack of the songs.  Sure, the music was still there, but I found my mind wandering.  The "swirl" - as I call it - was missing; this is the moment when the notes become visual, engrossing the mind with music.  Depth also become shorter and the soundstaging less enveloping than normal.

I tried a few other albums - Roxy Music, Dr. John, an Agalloch CD - and found that the quieter cuts fared better.  Once the dynamics cranked up, the bass would become plodding and the music unrefined, bringing down the system sound quality down several notches - turning my pride and joy into a sonic mess.  Adjusting the current down to 50mA didn't seem to make any difference either.

Conclusion:
I really, really wanted to like these tubes.  I mean they look great and I'm usually a champion of Chinese tubes, but - at least with this amplifier - I cannot recommend the Valve Art 350B.  Perhaps in push-pull or with a different transformer load, voltage, or current, or even cathode bias they would shine.  Or maybe I was asking too much out of them, but the SED 6L6GC in the same circuit sounded much better.


Review System:
VPI Aries with JMW 10.5i tonearm and SDS Power Supply
Dynavector 10X5
Cardas Cross 1M interconnects
Quicksilver preamplifier with Mullard short-plate 12AX7s, RCA 12FQ7s, Amperex 12AU7
Cardas Quadlink 5C 1M interconnects
Multi-Valve Stereo amplifier
Cardas Hexlink speaker cable
UREI 813A monitor speakers
VTI BL503 equipment rack